What are Vascular Doppler Measurements?
Doppler measurements of the peripheral arteries, particularly those in the legs, are an important qualitative diagnostic method to determine arterial vascular elasticity as part of a complete Peripheral Arterial Disease (PAD) diagnosis.
The primary assessment includes the determination of the number of “phases” in a Doppler waveform over one cardiac cycle, typically between one (abnormal) and 3 (good elastic vessel).
In the lower extremities, the arteries that are typically measured with Doppler include the Dorsalis Pedis, Posterior Tibial, Popliteal, and Femoral arteries. The most commonly measured arteries in the upper extremities include the Radial, Ulnar, and Brachial vessels.
Which Doppler Probe should be Used?
The requirement from the Doppler probe is to have an appropriate frequency that meets the measurement requirements. Thus, for the Doppler measurement of the smaller, more superficial vessels such as the DP or PT, a 10 MHz or 8 MHz probe is used, while for larger or deeper vessels, the 4 MHz probe is preferred.
Also, the requirement from the Doppler is to have Continuous Wave (CW) Doppler, direction sensitivity and bi-directional flow capabilities, audible output, and recording.
Above all, a complete color spectral analysis is a preferred option as it allows us to distinguish between forward and reverse blood flow clearly.
How to Perform Vascular Doppler Measurements
Performing vascular Doppler measurements requires proper training and skill to obtain accurate results.
Follow these steps to conduct Doppler measurements of peripheral arteries:
- Patient Preparation:
Ensure the patient is comfortably positioned, with the limb to be examined exposed and relaxed. Instruct the patient to avoid caffeine and smoking for a few hours before the test, as these can affect blood flow.
- Selecting the Doppler Probe:
Choose the appropriate Doppler probe based on the vessels to be measured. Use a 10 MHz or 8 MHz probe for smaller, more superficial vessels, and a 4 MHz probe for larger or deeper vessels.
- Applying Ultrasound Gel:
Apply a sufficient amount of ultrasound gel to the area where the Doppler probe will be placed. This helps in transmitting sound waves and improving signal quality.
- Locating the Arteries:
Identify the target arteries in the patient’s extremity. Common arteries include Dorsalis Pedis, Posterior Tibial, Popliteal, Femoral, Radial, Ulnar, and Brachial arteries.
- Proper Probe Placement:
Gently place the Doppler probe over the selected artery at an appropriate angle to obtain the best signal. Adjust the probe position if necessary to optimize the signal.
- Activating the Doppler:
Turn on the vascular device and select the appropriate settings, including selecting the correct Continuous Wave (CW) Doppler, direction sensitivity, and bi-directional flow capabilities.
- Listening for the Doppler Signal:
Listen for the Doppler signal through the device’s audible output. The presence of the signal indicates blood flow in the artery.
- Identifying Waveform Phases:
Pay attention to the Doppler waveform displayed on the device. Identify the number of “phases” in the waveform over one cardiac cycle. A phase is indicated by a Doppler waveform crossing the zero line. A tri-phasic waveform (3 phases) is typical of healthy and elastic arteries.
- Recording and Analyzing Results:
Record the Doppler waveforms and any relevant quantitative parameters provided by the Doppler device.
- Documenting the Findings:
Document the findings, including the interpretation and any quantitative measurements obtained during the Doppler examination.
This step-by-step guide for performing a Doppler measurement test is for informational purposes only. Healthcare professionals should rely on their expertise, clinical judgment, and institutional protocols for accurate administration and interpretation. Additional clinical information, patient history, physical examination, and other diagnostic tests may be necessary for comprehensive evaluation.
Benefits of Using the Falcon for Doppler Measurements
The Falcon is a cutting-edge physiologic diagnosis system designed for Doppler measurements of peripheral arteries. Utilizing the Falcon offers numerous benefits, making it an ideal choice for healthcare professionals:
- Complete Range of CW Doppler Probes:
The Falcon provides a wide range of Continuous Wave (CW) Doppler probes, including standard 4 MHz and 8 MHz frequencies. Additionally, it offers a 10 MHz probe suitable for very shallow and small vessels. This versatility ensures comprehensive coverage of all peripheral arteries.
- Full-Color Spectral Analysis:
Unlike many other Doppler systems in the market, the Falcon offers complete spectral analysis in full color. This advanced feature allows healthcare professionals to clearly distinguish between forward and reverse blood flows, reducing the chances of misinterpretation.
- Pre-configured Doppler Settings:
The Falcon simplifies the Doppler examination process by allowing users to pre-configure settings in the protocol. This streamlines the test procedure, ensuring consistent and efficient measurements.
- User-Friendly Interface:
The Falcon is designed with an intuitive user interface, making it user-friendly for medical professionals of all experience levels. The device allows users to modify the preferred sweep time display, scale, gain, filter, and sound volume according to their preferences.
- Quantitative Parameters for Improved Diagnosis:
In addition to qualitative waveform analysis, the Falcon provides a range of quantitative parameters. These parameters include Peak, Mean, and Diastolic velocities, PI, RI, S/D pulsatility indices, as well as rise time, and heart rate. The availability of these parameters enhances the accuracy of diagnosis and assessment.
- Streamlined Clinical Diagnosis:
The Falcon facilitates a seamless workflow from Doppler measurements to clinical diagnosis. The efficient design and features allow healthcare professionals to conduct comprehensive assessments in a fast and efficient manner.
- Enhanced Patient Care:
By using the Falcon for Doppler measurements, medical professionals can provide more precise and personalized care to their patients. Accurate assessments help in the early detection and monitoring of arterial diseases, contributing to better patient outcomes.
- Trusted Brand:
Viasonix, the manufacturer of the Falcon, is a trusted brand known for delivering high-end vascular systems and innovative medical technologies. Viasonix commitment to quality and performance makes the Falcon a reliable choice for Doppler measurements.
Doppler Measurement Limitations
While Doppler measurements play a crucial role in evaluating arterial vascular elasticity and detecting abnormalities in blood flow, it is important to recognize that Doppler alone may not be sufficient for a complete diagnosis.
Doppler measurements provide valuable information, but a comprehensive vascular assessment typically involves several other diagnostic tests to obtain a more thorough understanding of a patient’s vascular health:
- Importance of ABI (Ankle Brachial Index):
ABI is a critical test, which also uses Doppler measurements to assess lower extremity arterial circulation. It involves comparing blood pressure measurements taken at the ankles and arms. ABI helps in diagnosing PAD, determining its severity, and assessing the risk of cardiovascular events. It is an essential component of a comprehensive vascular assessment.
- Role of PPG (Photo-plethsymography):
PPG is another valuable non-invasive test used in vascular assessment. It measures changes in volume or blood flow within the arteries as a response to each heartbeat. PPG aids in evaluating peripheral arterial blood flow and allows assessment of the essential Toe-Brachial Index (TBI). It also assists in detecting arterial obstructions and in assessing the effectiveness of treatments or interventions.
- Pulse Volume Recording (PVR):
Pulse Volume Recording is yet another important test that complements Doppler measurements. PVR assesses changes in limb volume during the cardiac cycle, providing valuable information about arterial blood flow and detecting abnormalities such as arterial occlusions and peripheral artery disease.
- Exercise Stress Testing:
In some cases, Doppler measurements may not reveal abnormalities at rest but could be triggered by exercise or stress. Exercise stress testing evaluates blood flow and arterial function during physical activity, helping identify exercise-induced arterial insufficiency or other exercise-related vascular issues.
A complete vascular assessment involves integrating information from various diagnostic tests, clinical evaluation, and the patient’s medical history. The combination of Doppler measurements, ABI, PPG, PVR, and stress testing allows healthcare professionals to create a more accurate and personalized diagnosis, leading to appropriate treatment plans.
Expected Results of Vascular Doppler Tests
The interpretation of peripheral Doppler waveforms is a crucial aspect of the Doppler measurement process. Healthcare professionals focus on determining the number of “phases” present in the Doppler signal to gain valuable insights into arterial vascular elasticity and overall vascular health.
- Tri-Phasic Waveform (Normal):
A “normal” Doppler waveform is tri-phasic (or multi-phasic), characterized by at least three distinct phases. This waveform indicates a healthy and elastic artery. In a tri-phasic waveform, the Doppler signal exhibits a dominant forward flow followed by a smaller reverse flow section and then another small forward flow. This pattern is typically seen in healthy individuals with no significant vascular abnormalities.
- Bi-Phasic Waveform:
If the final small forward flow is not seen, the Doppler signal is considered bi-phasic. A bi-phasic waveform indicates a moderate decrease in arterial elasticity, suggesting the onset of arterial stiffness or mild arterial disease. While not as optimal as a tri-phasic waveform, a bi-phasic waveform still represents a relatively healthy arterial condition.
- Mono-Phasic Waveform:
In a mono-phasic Doppler waveform, only the initial forward flow is seen, and the reverse flow section is absent. A mono-phasic waveform indicates a further reduction in arterial elasticity and is often associated with moderate to severe arterial disease or stiffer arteries. The systolic peak in a mono-phasic waveform is also less sharp and becomes wider and rounded.
The assessment of Doppler waveforms is particularly valuable in monitoring the progression of arterial disease. As arterial disease advances, the arteries become stiffer, leading to changes in the Doppler waveform characteristics:
- As arterial disease progresses, the third flow phase in tri-phasic waveforms starts to disappear, and the waveform becomes bi-phasic.
- In more advanced stages of arterial disease, the second flow phase in bi-phasic waveforms also diminishes, resulting in a mono-phasic waveform.
Overview of Peripheral Arterial Disease of the Lower Extremity, Ali F. AbuRahma and John E. Campbell, Noninvasive Vascular Diagnosis, A.F. AbuRahma (ed.), Springer International Publishing AG 2017, Ch 21, pp 291-318
Lower Extremity PAD, Hirsch et al. 2005, ACC/AHA 2005 Guidelines for the Management of Patients With Peripheral Arterial Disease
Characterizing Triphasic Biphasic, and, Monophasic Doppler Waveforms: Should a Simple Task Be So Difficult?, Robert Scissons, JDMS 24:269–276 September/October 2008
2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease; A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines; Journal of the American College of Cardiology, Vol. 69, No. 11, 2017
Lower Extremity Arterial Physiologic Evaluations, Vascular Technology Professional Performance Guidelines, the Society for Vascular Ultrasound, 2019
Noninvasive Physiologic Vascular Studies: A Guide to Diagnosing Peripheral Arterial Disease, Robert Sibley et al, radiographics.rsna.org, Volume 37 Number 1, p 346-357.
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